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American vs Canadian Types of Radon Systems


What’s the difference?

Simply put, the Canadian type radon system has the radon fan mounted inside the basement with the vent pipe venting through the wall near the ground similar to a dryer vent. The American type system typically has the fan mounted on the exterior wall near ground level and the vent pipe runs up the side of the house past the roof. In every other way the two types of systems are the nearly the same. When well explained regarding the differences, pros and cons, and safety considerations, most homeowners choose to have the Canadian Type Radon Mitigation System installed.


Why is the Canadian Type Radon System Better?

A Canadian type radon system with the radon fan located indoors is better in several ways, compared to an American type system with the fan located outside the house, especially in cold weather climates. Prior to 2010 most Canadian radon mitigators installed radon systems following the American Radon Mitigation Standards and most of those systems had the radon fan mounted on the exterior of the home. Canadian homeowners and radon contractors noticed that during extended freezing temperatures, ice caps would form on top of the vent pipes blocking the air flow. 

How does that happen? The radon fan pulls warm moist air from below the ground which cools and condensates as it moves up the vent pipe. In freezing weather the air cools more and more the further it gets from the ground. The cooling moisture in the air condensates and collects as droplets as it comes in contact with the cold surface of the vent pipe and when cold enough the droplets freeze before they exit the pipe. The ice continues to form, building up and restricting air flow or totally stopping the air flow. 


When an ice cap forms, radon mitigation ceases because there is no air flow even though the radon fan continues to run. This poses a radon safety hazard as the radon will return to pre-mitigation high levels until temperatures warm up long enough to eventually melt the ice and the air flow is resumed.













The freeze thaw process also takes a heavy toll on the service life of radon fans. According to my estimate from having replaced hundreds of failed radon fans, exterior radon fans in central New York have roughly one third the service life - 5 to 12 years, compared to radon fans located in a basement or attic space which last much longer, 20 to 30 years. I have replaced many dozens of exterior mounted radon fans from less than 1 year old to less than 10 years old. I have never seen an exterior mounted radon fan last for 20 years, however I have seen dozens of basement or attic mounted radon fans still operational after 20 to 30 years.

Pros - Indoor Radon Fan vs Outdoor Radon Fan

  • Indoor fan radon systems are safer due to being more reliable; they will not freeze up and stop working when it gets really cold.

  • Indoor radon cost fans last about 3 to 4 times as long. Replacing a radon fan typically costs $250 to $500.

  • Radon mitigation systems with indoor radon fans are more efficient. They typically use much less less pipe and have fewer bends in the pipe, which equates to less air flow resistance and less energy required to move a given amount of air.

  • Due to greater efficiency, systems with interior mounted fans can operate effectively with smaller size fans which are quieter, use less energy and have a lower replacement cost.

  • Indoor radon fans are less expensive to operate, saving money on your electric bill.

  • Indoor radon fan systems cost less to install. Typical savings of $100 to $300 or more due to less in materials and labor costs.

  • Canadian type radon mitigation systems are much more aesthetically pleasing. No fan mounted on the wall and pipe running up the exterior to above the roof.

  • Radon systems with interior mounted fans typically have more options for location of the radon vent pipe discharge since it is similar to a dryer vent.

Cons - Indoor Radon Fan Benefits vs Outdoor Radon Fan:

  • Indoor fan radon are much less common in central New York and many home owners, realtors and home inspectors are ignorant of the facts regarding Canadian Type Radon Systems.

  • Uninformed persons often make false statements regarding indoor radon fans such as "Radon fans are not allowed to be in a basement, they are illegal, they are unsafe, they are against code, they are  not properly installed.

  • When selling a home with a Canadian type radon system for the above reasons, the radon fan located in the basement may be an issue if the well intentioned realtor or home inspector tells the buyer it is unsafe or against code and the fan should be moved to the exterior.

So Why the Controversy?

There is a contradiction between the Canadian and  American Radon Mitigation Standards. The first recommending radon fans be placed in basements and the second states radon shall not be installed in basements. The old and current American EPA and National Radon Mitigation Standards of Practice do not allow radon fans to be placed inside basements, below or in the living areas of the home for "supposed potential" safety reasons. In contrast Health Canada, Canada's agency similar to the EPA, recommends that radon fans should preferably, be placed in basements, typically in a mechanical room or unfinished part of the basement.

Quote from Health Canada's Radon Reduction Guide For Canadians - "The sub-slab depressurization pipe can be vented at either the roof level or ground level of the home. The fan can be placed in the basement or an area outside of the living space such as in a garage or attic. If the fan is placed inside the living space of the home"

In contrast the EPA's Consumer Guide To Radon Reduction states, "The exhaust fan must not be located in or below a livable area. For instance, it should be installed in unconditioned space" 










Picture courtesy of Health Canada - Radon Reduction Guide For Canadians

Canadian Mike Holmes standing in front of a radon fan installed in a basement showing an example of a properly installed radon system. Video link





















New York State Requirements for Radon Mitigation Systems

As of this writing - 2/12/2024, New York State does not certify or license radon mitigators and there is no requirement for Radon contractors or mitigation firms to be certified or licensed. In fact, there is no state regulatory oversite regarding radon mitigation, meaning, homeowners or radon mitigation contractors or general contractors can install any type of radon mitigation system they like, as long as it complies with applicable local building codes. I've checked and there are no radon mitigation specific code requirements for Manlius, Fayetteville or Syracuse and there are none that I'm aware of in any other central New York locality.










Other States Requirements for Radon Mitigation

Some other states do have require licensing and certification for radon mitigation, such as Connecticut, New Jersey and Pennsylvania.

See related message from the New York state radon office:


Click here too view full page:       "...New York State does not regulate radon service providers, however, certification through one of the national organizations is recommended."

Misinformation Abounds in New York re Radon Mitigation 

Unfortunately in New York there is no lack of misinformation regarding radon mitigation, radon testing and radon in general. I have heard and am aware of many realtors, home inspectors and radon mitigation contractors who have repeatedly made false statements often opposite of what the truth is. Following  are some common mistruths often stated:

  • Radon fans installed in a basement are against the law, or against building code

  • Redon vent pipe that 


heard   what is required by NY State law, local codes, what is safe and not safe, what is proper and not proper, 

What do the Radon Fan Manufacturers Say?

The three major radon fan manufactures were asked about how their fans performed when located outside in cold weather environments and any concerns or installation instructions that they would have. Here are their responses:

Festa Radon Technologies Co: “Festa fans are rated for outdoor use. Festa has no concerns about our fans being placed outdoors in cold temperatures provided they are installed in a vertical position”

Brief History – The Cowboy Days of Radon Mitigation

Canada actually followed the original American Radon Mitigation Standards, set by the EPA back in 1993. At the time, in the early days of radon mitigation, the EPA scrambled to put together some type of standards for mitigation of radon since contractors and homeowners were throwing together all type of things to mitigate radon including all types of unsuitable fans and improper vent materials. For example using flexible plastic dryer vent attached to fans using tape. Many of these cobbed together components fell apart in no time and became safety hazards. The EPA for the most part copied the Plumbing Vent Code intended for venting sewer gas and used that for the standard to vent radon radon gas. Today, in 2024 the American National Standards of Practice for Radon Mitigation have changed very little.

An excerpt from Canada Health publication “Reducing Radon Levels in Existing Homes: A Canadian Guide for Professional Contractors” Section 9.3 – Fan Location

... “In the early days of radon mitigation, prior to development of the US mitigation Standards, the fans used were not airtight, and leaked some of the exhaust air from their casings. A variety of ducting materials was also used and not all joints were airtight. As a result, best practice was to place the fan and discharge piping outside the building envelope. The interior piping was then under negative pressure, so neither fan nor duct leakage would enter the building. Fans located outside the building envelope are required by US mitigation standards.

In-line centrifugal fans specifically designed for radon mitigation are now available. Some airtight fan designs are available with sealed joints; some have the casing joints and electrical connections located on the suction side of the fan, so leakage from the fan is not a concern. Plastic plumbing pipe is now used routinely for the suction and exhaust ducting, with airtight solvent welded joints in the piping and airtight rubber plumbing couplers to the fan.

As properly installed fans and ducting will not leak soil air and radon into the building, the fan no longer needs to be located outside the building envelope, but can be mounted inside the building. If this is combined with a grade level discharge, almost the entire system can be inside the thermal envelope. In cold climates, this eliminates concerns about condensation or frost in the fan or piping, as only a short length of discharge pipe outside the house will be exposed to colder temperatures.

A fan should be installed so that the flow is vertical, so that any condensation in the system will drain through the fan, rather than pooling in the casing. To reduce vibration and noise transfer to the building, it should be connected to the piping with airtight rubber plumbing couplers that hold the fan 1 cm from the pipe. If the supply and discharge pipes are firmly mounted, the fan can simply be attached to the pipes by the couplers without other support. If it is attached to a wall, a masonry or concrete wall will give lower noise than an internal framed wall.

If the selected fan is not airtight, it must be mounted outside the building envelope. In cold areas, an outside fan is at risk from premature failure due to moisture in the exhaust air condensing, and freezing in the fan. To prevent this, a fan mounted on the exterior of a building should be placed inside an enclosure (commercially available enclosures are available) for cold weather protection. A condensation by-pass should be installed to collect and divert condensation in the discharge pipe around the fan. To prevent the condensate from freezing, the discharge should be led to the soil through an insulated pipe, or in very cold areas, back into the fan suction pipe. The suction pipe inside the house must be sloped so that condensate passing through the fan can drain back to the sub-slab fill with no low spots where condensate can accumulate.”

Source Location: Canadian Radon Mitigators Installation Guide.pdf (

Mike Holmes on Radon video_edited.jpg

Quotes from New York State Department of Health web page: "NYS does not certify or license radon mitigators." "Radon mitigation firms may be certified..."

Quotes from New York State Department of Health web page: "Choose a contractor to fix a radon problem just as you would choose someone to do other home repairs..." "New York State Department of Health does not regulate radon services."

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